Mid-infrared Fourier-transform spectrometer based on metamaterial lateral cladding suspended silicon waveguides

TL;DR

This paper presents a novel mid-infrared Fourier-transform spectrometer using metamaterial-cladded suspended silicon waveguides, enabling operation beyond 4 μm with low loss and high spectral resolution for environmental and space applications.

Contribution

It introduces a metamaterial-cladded suspended silicon waveguide platform that overcomes SOI limitations in the mid-infrared, enabling compact, low-loss, high-resolution spectrometry near 5.5 μm.

Findings

Propagation loss below 2 dB/cm between 5.3μm and 5.7μm

Spectral resolution of 13cm-1 achieved

Operates near 5.5μm wavelength

Abstract

Integrated mid-infrared micro-spectrometers have a great potential for applications in environmental monitoring and space exploration. Silicon-on-insulator (SOI) is a promising platform to tackle this integration challenge, due to its unique capability for large volume and low-cost production of ultra-compact photonic circuits. However, the use of SOI in the mid-infrared is restricted by the strong absorption of the buried oxide layer for wavelengths beyond 4 {\mu}m. Here, we overcome this limitation by utilizing metamaterial-cladded suspended silicon waveguides to implement a spatial heterodyne Fourier-transform (SHFT) spectrometer operating near 5.5{\mu}m wavelength. The metamaterial-cladded geometry allows removal of the buried oxide layer, yielding measured propagation loss below 2 dB/cm between 5.3{\mu}m and 5.7{\mu}m wavelengths. The SHFT spectrometer comprises 19 Mach-Zehnder interferometers with a maximum arm length imbalance of 200 {\mu}m, achieving a measured spectral resolution of 13cm-1 and a free-spectral range of 100 cm-1 near 5.5{\mu}m wavelength.